This relates generally to imaging devices, and more particularly to imaging devices that use imaging sensors that gather scene image data using an electronic rolling shutter.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Image sensors may be formed from a two-dimensional array of image sensing pixels. Each pixel receives incident photons (light) and converts the photons into electrical signals. Image sensors may program the duration of the exposure of a pixel to incident light before reading the electrical signals produced by the pixel. The period of time wherein a pixel is exposed to incident light after being reset is called the integration time. A pixel may be reset, after the electrical signal it produced has been read. After a pixel is reset, it may be used to collect light information about a scene, again.
The timing and duration of pixel integration, readout, and reset operations may be directly or indirectly controlled by control circuitry. The control circuitry may respond to a trigger control signal. The response of control circuitry to a trigger control signal may differ based on its operating mode, which may be determined by the user or by constraints of particular system implementations.
As the amount of data processed by a camera system increases, subtle differences in the response of control circuitry to a trigger control signal may determine the performance of the system. An imaging system may use multiple image sensors in one or more camera devices to capture images with a large field of view. An imaging system may use multiple cameras to capture images at different frame rates or at different resolutions, to gain insight into different aspects of the imaged scene while minimizing the amount of data needed to capture the relevant information. Embodiments of such multi-camera systems may be used in autonomous vehicles which use both visible and infrared cameras to capture information about the surrounding scene. Embodiments of such multi-camera imaging systems may be used in multispectral or hyperspectral imagers, which capture data about multiple bands of the electromagnetic spectrum.
Due to their high system throughput, the usability of a multi-camera system may be impeded if its control circuitry's responses to trigger control signals are non-deterministic. Due to their applicability in imaging dynamic scenes such as the environment around an autonomous vehicle, the efficacy of multi-camera systems may be lessened if the systems are incapable of varying frame rates without any image quality artifacts.
It would therefore be desirable to provide an improved operating mode or response to a trigger control signal for multi-camera systems.